I've been reading a lot about mash techniques and I'm not clear on the definition of a protien rest. Is this just removing the mash from heat after it reaches the desire temperature or maintaining the desired temperature for a specified period of time?

The protein rest, while not always performed, serves to degrade long-chained proteins into simpler proteins more beneficial for the brewing process. It is especially helpful when using under modified malts whose proteins require further degradation or when using over 10% starch adjuncts in the mash. The mash is stabilized at 122